Generally, a plasma display panel (PDP) has a three-electrode surface-discharge structure. The PDP having the three-electrode surface-discharge structure includes front and rear substrates. A discharge gas is sealed between the two substrates.
The front substrate has sustain electrodes and scan electrodes that extend in one direction on the inner surface of the front substrate. The rear substrate is spaced apart from the inner surface of the front substrate and has address electrodes that extend in a direction intersecting the direction of the sustain and scan electrodes.
In this PDP, whether or not a discharge is generated is determined by an address discharge between the sustain electrodes and the address electrodes that are controlled independently. Then, images are realized by a sustain discharge between the sustain electrodes and the scan electrodes located on the inner surface of the front substrate.
The PDP generates visible light by using a glow discharge. After the glow discharge is generated, visible light reaches human eyes through several steps. If the glow discharge is generated, gas is excited by the collision of electrons against gas and then vacuum ultraviolet rays are generated from the excited gas. The vacuum ultraviolet rays collide against phosphors in discharge cells. As a result, visible light is generated and reaches the human eye through the transparent front substrate.
While passing through the above steps, input energy applied to a cathode and an anode is lost due to inefficiencies. To compensate for the lost energy, the glow discharge is generated by applying a voltage higher than a discharge firing voltage between the two electrodes. In order to fire the glow discharge, a considerably high voltage is required.
Once discharge is generated, the voltage distribution between the cathode and the anode is distorted due to a space charge effect caused by dielectric layers in the periphery of the cathode and the anode. A cathode sheath region, an anode sheath region, and a positive column region are formed between the two electrodes.
The cathode sheath region is a region in the periphery of the cathode, in which most of the voltage applied between the two electrodes is consumed. The anode sheath region is a region in the periphery of the anode, in which some of the voltage is consumed. The positive column region is a region between the cathode sheath region and the anode sheath region, in which almost no voltage is consumed.
The electron heating efficiency of the cathode sheath region depends on the secondary electrode coefficient of an MgO protective film that is formed on the surface of the dielectric layer. In the positive column region, most of the input energy is consumed for electron heating.
The vacuum ultraviolet rays are generated when xenon (Xe) gas is changed from an excitation state to a ground state. The excitation state of Xe gas is generated by the collision between Xe gas and electrons.
In order to increase the luminescence efficiency, which is the ratio of visible light to the input energy, the rate of collision between Xe gas and electrons must be increased. In order to increase the rate of this collision, the electron heating efficiency must be increased.
Most of the input energy is consumed in the cathode sheath region. In the positive column region, consumption of the input energy is low and the electron heating efficiency is high. Accordingly, a higher luminescence efficiency can be obtained by a larger positive column region. The positive column region is also called a discharge gap.
The change in the E/n, the ratio of the electric field E across the discharge gap to the gas density n, and the ratio of electron consumption to the overall number of electrons have been studied. At the same electric field to gas density ratio, E/n, the ratio of electron consumption to the total number of electrons is increased with an increase in xenon excitation Xe*, xenon ions Xe+, neon excitation Ne*, and neon ions Ne+.
Further, it has been known that, at the same ratio E/n, the higher the partial pressure of Xe, the lower the electron energy. That is, if the electron energy is decreased, the partial pressure of Xe is increased. As a result, the ratio of electron consumption for the excitation of Xe* is higher than electron consumption for xenon ions Xe+, neon excitation Ne*, or neon ions Ne+. Accordingly, the luminescence efficiency is enhanced in the case of Xe* excitation.
As described above, an increase in the positive column region results in an increase in the electron heating efficiency. Further, increase in the partial pressure of Xe results in the increase of the electron heating efficiency of electrons consumed for the excitation of Xe. Accordingly, an increase in the positive column region and an increase in the partial pressure of Xe, both result in the increase of the electron heating efficiency, thereby enhancing the luminescence efficiency.
However, increase in the positive column region or increase in the partial pressure of Xe, result in an increased discharge firing voltage, which causes the manufacturing cost of the PDP to be increased. Therefore, an increase in the positive column region or the partial pressure of Xe must be achieved under low discharge firing voltage, in order to enhance the luminescence efficiency. For the same discharge gap and partial pressure of Xe, the discharge firing voltage required for the opposing electrode structure is lower than the discharge firing voltage required for the surface discharge structure.